Many pieces of construction equipment use hydraulics to control the functions performed by the equipment. For example, many pieces of construction equipment use hydraulics to control the brakes. If pressure is lost in the hydraulic system, it is important that the brakes continue to operate so that the operator can stop the piece of equipment.
According to one aspect of the present invention, a vehicle is provided including a frame, a plurality of traction devices configured to propel the frame on the ground, a plurality of hydraulic actuators, brakes configured to control the speed of the vehicle, and a hydraulic control system. The hydraulic control system includes a pressure source providing pressurized hydraulic fluid, a load sense system detecting the maximum pressure needed by the plurality of hydraulic actuators during operation of the vehicle, and a plurality of hydraulic controls controlling the supply of pressurized fluid to the plurality of hydraulic actuators. The plurality of hydraulic controls uses the maximum pressure detected by the load sense system to regulate the pressure of the hydraulic fluid provided to the plurality of hydraulic actuators. The hydraulic control system further includes a pressure source control coupled to the load sense system and pressure source to control the pressure output from the pressure source based on the maximum pressure detected by the load sense system, a load boost input to the load sense system that maintains the maximum pressure detected by the load sense system at least at a predetermined pressure, and a hydraulic fluid accumulator supplying pressurized fluid to the brakes. The predetermined pressure is sufficient to provide a charge for the hydraulic fluid accumulator sufficient for a predetermined number of applications of the brakes.
According to another aspect of the present invention, a vehicle is provided including a frame, a plurality of traction devices configured to propel the frame on the ground, a plurality of hydraulic actuators, and a hydraulic control system. The hydraulic control system includes a hydraulic pump providing pressurized hydraulic fluid and a load sensor configured to detect the maximum pressure needed by the plurality of hydraulic actuators. The load sensor provides a signal indicative of the maximum pressure. The hydraulic control system further includes a plurality of pressure compensators provided for the plurality of hydraulic actuators. Each of the pressure compensators provides pressurized fluid to at least one corresponding hydraulic actuator based on the signal from the load sensor and the necessary load pressure from the corresponding hydraulic actuator. The hydraulic control system further includes a signal regulator providing an input to the load sensor to maintain the signal provided by the load sensor above a predetermined level.
According to another aspect of the present invention, a vehicle is provided including a frame, a plurality of traction devices configured to propel the frame on the ground, a plurality of hydraulic actuators, and a hydraulic control system. The hydraulic control system including a pressure source providing pressurized hydraulic fluid, a plurality of hydraulic controls regulating the supply of pressurized fluid to the plurality of hydraulic actuators, a load sensor including a plurality of comparators receiving inputs from the plurality of hydraulic actuators to detect a maximum pressure needed by the plurality of hydraulic actuators and providing a hydraulic signal indicative of the maximum pressure, a load signal regulator providing an input to at least one of the plurality of comparators at a predetermined pressure to maintain the hydraulic signal above a predetermined minimum, and a pump control receiving the hydraulic signal from the load sensor and controlling the output pressure from the source of pressurized fluid.
Additional features of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the presently perceived best mode of carrying out the invention.